The heat transfer analysis plays an important role in the temperature prediction
of insulated steel members exposed to fire conditions. Based on the results of a
previous experimental work, made in intumescent-coated protected elements, the
intumescent effective thermal conductivity temperature variation was estimated.
An analytical approach, based on the one-dimensional heat transfer parabolic
partial differential equation through the insulation, considering a nonhomogeneous
(time-varying) boundary condition at fire interface and a lumped
capacitance at the insulation-steel interface, is presented. Solutions are
established with temperature independent thermal properties and then extended
to temperature dependent thermal properties. These solutions are compared with
numerical results performed by finite element method using Matlab for different
values of insulations thicknesses and steel section factors.